Well treating fluid



Patented Feb. 29, 1944 WELL TREATING FLUID .Albert L. Frye and William M. Dobson, Long Beach,

CaliL, assignors to Richiield Oil Corporation, Los Angeles, Callfl, a corporation of New Jersey No Drawing. Application October 1, 1941,

Serial No. 413,153

8 Claims. (01. 252-855).

This invention relates to a well treating fluid and more particularly to a fluid for improving bottom hole conditions in a well.

Frequently the production of a well falls off due to abnormal bottom hole conditions, This may be caused by any one of several conditions, such as asphaltic or waxy accumulationathe presence of scale of an inorganic nature, the presence of drilling mud or other materialused in drilling in the well, the presence of oil or watersoftened shales or the presence .of brackish water.

Several methods have heretofore been available for cleaning up such bottom hole conditions and increasing the production of the well. These methods, however, have been subject to one or more of several objections. They have been difilcult or'expensive to apply, or the results have been unsatisfactory. These. methods include various mechanical treatments, such as under-reaming, the use of wall scratchers, the use of perforation cleaning knives and the use of wax scratchers; and chemical means, such as treating with hydrocarbon solvents, acids, alkalis and surface active chemicals, such as sulfated alcohols; and physical treatments, such as washing with well fluids or chemicals, or melting with steam or other sources of heat.

The chief defects of the mechanical treatments have been their high costs and their inability to reach the face of the producing formation due to the presence of a liner, a gravel pack or both in-the hole. The-chemical treatments have, in some instances, resulted in-the production of more water and no-increase in the production of oil The chief defect of the physical treatments has been their lack of permanence.

The presentjinventio'n comprises a well treating fluid for improving bottom hole conditions by means of which more satisfactory results are obtained. It may be used either alone or in conjunction with one or more of the mechanical treatments above outlined. The invention comprises the use of a water-in-oil emulsion that will either dissolve or emulsify the objectionable substances found in a well bottom or on the face of the producing formation and thereby permit ready removal of these substances from the well.

To accomplish these ends the fluid must be capable of dissolving asphaltic or waxy accumulations, dissolving mineral scales, disintegrating drilling mud and oil or water-softened shales the formations so that they may be more readily cleaned out by the crude oil.

To provide a composition capable of producing these results we employ an 011 base fluid which, being miscible with crude oil, will not block further production as a water base fluidtends to do. The composition, however, also includes. an aqueous phase, and we employ a water-in-oil emulsion so compounded that the dispersed chemicals in the aqueous phase can readily rupture the oily fllm of the dispersing phase when the latter is in contact with shales, clays, inorganic scales and water. This aqueous phase includes essentially a mineral acid, such as hydrochloric acid, sulfuric acid, nitric acid, or the like, to attack clays shales and calcareous scale.

Further, the composition includes a dispersed, colloidal hydrated silicate such as bentonite or montmorillonite. Colloidal hydrated silicates generally, of magnesium and of aluminum for example, both natural clays and synthetics, are

this refinery by-product has some capacity as an emulsifying agent and as a solvent for gums and waxes.

The composition may also include an organic acid of the acetic acid series, to promote emulsion fluidity and stability and to intensify the attack on and disintegration of clays and shales. It may'also include a chlorinated hydrocarbon, to increase the specific gravity of the fluid and to aid in the dissolving of waxes and gums. The chlorinated hydrocarbons useful in the composition include tri-chloroethylene but in placeof it we may employ the mono, di, tri, tetra and hexa chlorides of the paraiiin, olefine and acetylene series. It may also include one or more, preferably several, additional emulsifying agents or protective colloids to stabilize the solution.

\ These may include interracial (between oil and water) active agents such as the di-octyl ester of and lowering the surface tension of fluids lost t6 sodium sulphosuccinic acid, colloidally dispersed sulfur and hydroxy aromatic hydrocarbons such as cresyllc. acid.

While the sulfated and sulfonated hydrocarbons described are eilici'entemulsifying agents, we find it advantageous to use additional emulsiiying agents to make it possible to hold more water in the dispersed stage. Moreover, the hydrated silicates such as bentonitic clays form emulsions which are not entirely stable in the presence of strong mineral acid, used in our composition to attack clays, shales and calcareous scale, and it is therefore advantageous to use additional emulsifying agents. The interracial active agents mentioned sometimes tend to invert the emulsion under bottom hole conditions and the sulfur sometimes tends to form a tough emulsifying film. The phenols, such as cresylic acid, strongly promote the stability and tightness of the emulsion. If the emulsion tends to thicken in the well due to the picking up of bentonitic clays, cresylic acid may be used-to thin and reactivate it. Thus, the joint use of two or more of these additional emulsifying agents offers more than additive advantage in that such agents modify each other as well as the emulsion.

As an interfacial active agent, which is both water and oil soluble,'we preferably employ the di-octyl ester of sodium sulphosuccinate, but we may employ amines, ethers, esters or salts of suboughly washed with the fluid by means of a pressure washer. Or, agitation in the region to be treated can be had by circulation of the fluid, by movement of tubing swabs, or like expedients, in the region to be treated. Effective agitation in this region improves the-eflicacy of our composition. The composition of our invention when, as usually is the case, substantially heavier than water displaces the well fluid. The specific gravity of the composition, however, may be adjusted so that it is heavier, equal to or lighter than the fluids found in the well. This enables it to displace the well fluids, to mingle with them or to float on top of them depending upon the stituted aliphatic or aromatic and/or sulfonated' acids. We may also employ fatty acid alcohols. Such agents materially aid in the emulsiflcation, speed the attack on both organic and inorganic material and increase the fluidity of the composition. In some cases we may employ hydroxyaromatic hydrocarbons, such as phenol, cresylic acid or cresol, xylenol or methyl ethyl phenol. These speed the attack on either organic or incondition in the well to be treated and the location within the well at which the treating fluid is desired. Being miscible with crude oil it will not tend to form a separate layer. It also emulsifles with water without being aflected by the dissolved or suspended materials in the water and therefore will not separate in the presence of brackish water.

The conditions in the bottom of the well are improved, where abnormal conditions exist, by the dissolution of the heavier hydrocarbon fractions, such as asphalt or wax, the dissolution of inorganic scales, and the disintegration of oil or water-soaked muds and shales. When these ma terials are disintegrated they readily become suspended by any agitation of the fluid and thus can be brought to a condition. such that they can be readily pumped i'rom the well in suspenorganic solids and control the stability of the emulsion.

In .the presence of high concentrations of electrolytes, colloidally dispersed sulfur is employed as an emulsion stabilizer with special advantage. The use of too much sulfur. however, slows down or prevents the attack on clays or shales. An organic acid of the acetic acid series, such as acetic acid, propionic acid or, the like may also be employed to promote emulsion fluidity and stability. Where high concentrations or large amounts of mineral acids are employed, the use ,of an organic acid of the acetic acid series is particularly advantageous.

In some instances, we may also employ an interfacial active agent which is either insoluble or only slightly soluble in oil. As an example we may employ small quantities of the sodium salt of an alkylated aryl sulfonic acid. This increases the speed of attack and disintegration of clays and shales but the use of too great a quantity tends to invert the emulsion. We may also employ molecularly dehydrated phosphates, such as the sodium or potassium salts of hexametaphosphates or acid pyrophosphates, to stabilize the emulsion in the presence of calcium or similar I cations.

The materialsfforming our compositionare mixed in a high speed mixer or dispersion mill,

being added with advantage substantially in the order stated. Emulsiiication may be aided 'by heating to a temperature of from 120 to 140 F.

, The resulting fluid, the composition of our insion in the fluid. The presence of water soluble interfacial active agents permits the composition to pass readily into the brackish waters of the formation thereby lowering the interfacial tension of these waters so 'that they can be more readily cleaned out by the crude oil. The material is also non-corrosive to ordinary metal equipment in the well although in many instances'it is acidic.

Specific examples of compositions prepared within the scope of the present invention follow:

Parts by weight 1. Oil base (recovered from acid sludge) 47.25 2. Glacial acetic acid 10.17 3. 'I'ri-chloroethylene 7.15 4. Di-octyl ester of sodium sulphosuccinic acid 0.016 5. Cresylic acid (technical) 0.81 6. 5% aqueous suspension of bentonite 1.62 'I. Concentrated hydrochloric acid (technical) 3.75 8. Water 29.08

1. Oil base 52.30 2. Sulfur 1 0.21 3. Tri-chloroethylene 1.60 4. Cresylic acid 1.04 5. Glacial acetic acid 3.40 6. Di-octyl ester of sodium sulphosuccinic acid 0.02 '7. 5% aqueous suspension of bentonite- 1.01 8. Sodium hexametaphosphate 0.0004 9. Concentrated hydrochloric acid 7.60 10. Water 32.70

Parts by weight 1. 011 base 43.40 2. Di-octyl ester of sodium sulphosuccinic acid 0.11

3. Petroleum hydroxy aromatic phenols As examples of variation in the quantities of the various ingredients the following table is iven:

1.- The herein described product consisting of Y a water-in-oil emulsion comprising a water washed sludge derived from the treatment of a light'petroleum hydrocarbon with sulfuric acid, a lower member of the acetic acid series, a mineral acid capable of attacking clays, shales, and calcareousscale, a dispersed colloidal hydrated silicate, and water.

2. The herein described product consisting of a water-in oil emulsion comprising a water washed sludge derived from the treatment of a light'petroleum hydrocarbon with sulfuric acid. a lower member of the acetic acid series, a mineral acid capable of attacking clays, shales, and. calcareous scale, a material selected from the group consisting of mono, di, tri, tetra, and hexa chlorides of the paraflln, oleflne and acetylene series, a dispersed colloidal hydrated silicate, and

water. a

3. The herein described product consisting of a water-in-oil emulsion comprising a water washed sludge derived from the treatment of a light petroleum hydrocarbon with sulfuric acid, a. lower member of the acetic acid series, a mineral acid capable of attacking clays, shales, andcalcareous scale, an oil and water soluble interfacial agent selected from the group consist- Parts by weight except as noted Material Mini- Maximum mum 1 Oil base 35.0 35.3 2 Oil-and-water soluble interracial active agent 0. 016 0. l2 3 Hydroxy aromatic phenol 0. 80 l. 05 4 Chlorinated hydrocarbon 1. 00 i1. 00 5 Sulfur 0. 056 0. 21 6 Glacial acetic acid 3. 40 i5. 5 7 Aqueous suspension of colloidal hydrated silicates 0. 69 1.62 containing suspended solids. 0. 0035 0. 081 8 Concentrated hydrochloric acid.. 3. 75 7. 90 9 Water 17. 5 41. 8 10 Sodium hexametaphosphate in bentonite... 0. 02 0. 04 11 Sodium hexametaphospliate in water (parts per million parts of water) 3 10 12 Water soluble interracial active agent (percent based on weight of water) 0. 222 0.222

employ any sulfated and sulfonated derivatives of hydrocarbons and throughout the following portion of the specification and claims the term sulfated derivatives of hydrocarbons" is used to designate'such materials.

In using the fluid in treating abnormal bottom hole conditions, the results heretofore enumerated are obtained because the solution is miscible with crude oil and will therefore not plug the pores of the producing formation. At the same time it emulslfles with saline waters and therefore tends to produce a homogeneous fluid at the bottom of the well. It also aids in the penetration or disintegration of the asphaltic, or waxy accumulations at the bottom of the hole. It thus is capable of attacking waxy or gummy stituted aliphatic, aromatic and sulfonated acids. fatty acid alcohols and hydroxy aromatic hydrocarbons, a dispersed colloidal hydrated silicate, and water.

4. The herein described product consisting of a water-in-oil emulsion comprising a water washed sludge derived from the treatment of a light petroleum hydrocarbon with sulfuric acid, a lower member of the acetic acid series, a mineral acid capable of attacking clays, shales, and cal careous scale, an oil and water soluble interfacial agent selected from the group consisting of amines, ethers, esters and salts of substituted aliphatic, aromatic and sulfonated acids, fatty acid accumulations, inorganic scales, mud or shale and brackish water and has no tendency to form a coating over formationareas, due to inability ,to attack any one of the conditionswhich produces abnormal bottom hole conditions. Such tendency would otherwise lead to the formationof a coating and thus would prevent eflective alcohols and hydroxy aromatic hydrocarbons, a dispersed colloidal hydrated silicate, a material selected from the group consisting of mono, di, tri, tetra, and hexa chlorides of the paraflin, oleflne and acetylene series, and water.

5. The herein described product consisting of a water-in-oil emulsion comprising a water washed sludge derived from the treatment of a light petroleum hydrocarbon with sulfuric acid, acetic acid, hydrochloric acid, an oil and water soluble interfacial agent selected from the group consisting of ethers, esters and salts of substiw tuted aliphatic, aromatic and sulfonated acids, fatty acid alcohols and hydroxy aromatic hydrocarbons, a dispersed colloidal hydrated silicate, and water. a

6. The herein described product consisting of a water-in-oil emulsion comprising a water washed sludge derived from the treatment of a light petroleum hydrocarbon with sulfuric acid, acetic acid, hydrochloric acid, an oil and'water soluble interfacial agent selected from the group consistingof ethers, esters and salts of substituted aliphatic. aromatic and sulfonated, acids, fatty acid alcohols and hydroxy aromatic hydrocarbons. a dispersed colloidalhydrated silicate, a

material selected from the group consisting of mono. di, tri, tetra, and hexa chlorides of the parafiin, olefine and acetylene series, and water.

7. The herein described product consisting o! a water-in-oil emulsion comprising a water washed sludge derived from the treatment 0! a light petroleum hydrocarbon with sulfuric acid,

I a lower member of the acetic acid series, an oil hydrocarbons.

trichloroethylene, hydrochloric acld,"a dispersed colloidal hydrated silicate, and water.

8. The herein described product consisting of a water-in-oil emulsion comprising a water washed sludge derived from the treatment of a light petroleum hydrocarbon with sulfuric acid, acetic acid, hydrochloric acid, di-octyl ester of sodium sulfosuccinate, dispersed bentonitic clay,

w and grater.

WILLIAM M. DOBSON. ALBERT L. FRYE. 

